Integrally blow-moulded bag-in-container having a bag anchoring point; process for the production thereof; and tool thereof

ABSTRACT

The invention is an integrally blow-moulded bag-in-container obtainable by blow-moulding an injection moulded multi-layer preform. The bag-in-container includes an inner layer forming the bag and an outer layer forming the container, and a single opening, the mouth, fluidly connecting the volume defined by the bag to the atmosphere. The container further includes at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere, wherein the bag is anchored to the outer layer at at least one point remote from the single opening and interface vent. The invention also relates to a process and a mould for the production of the blow-moulded bag-in-container.

This application is a divisional application of U.S. Ser. No.12/450,904, filed on May 24, 2010, which was a 35 U.S.C. §371 nationalphase conversion of PCT /EP2008/054768, filed on Apr. 18, 2008, whichclaims priority to U.S. application Ser. No. 11/785,748, filed on Apr.19, 2007.

FIELD OF THE INVENTION

The present invention relates in general to new developments indispensing bag-in-containers and, is particular, to anchoring means forfixing the bag to the container at at least one point in order tostabilize it during collapse thereof upon use. It also relates to amethod and tool for producing said bag-in-containers.

BACKGROUND OF THE INVENTION

Bag-in-containers, also referred to as bag-in-bottles or bag-in-boxesdepending on the geometry of the outer vessel, all terms consideredherein as being comprised within the meaning of the termbag-in-container, are a family of liquid dispensing packaging consistingof an outer container comprising an opening to the atmosphere—themouth—and which contains a collapsible inner bag joined to saidcontainer and opening to the atmosphere at the region of said mouth. Thesystem must comprise at least one vent fluidly connecting the atmosphereto the region between the inner bag and the outer container in order tocontrol the pressure in said region to squeeze the inner bag and thusdispense the liquid contained therein.

Traditionally, bag-in-containers were—and still are—produced byindependently producing an inner bag provided with a specific neckclosure assembly and a structural container (usually in the form of abottle). The bag is inserted into the fully formed bottle opening andfixed thereto by means of the neck closure assembly, which comprises oneopening to the interior of the bag and vents fluidly connecting thespace between bag and bottle to the atmosphere; examples of suchconstructions can be found infer alia in U.S. Pat. Nos. 3,484,011,3,450,254, 4,330,066, and 4,892,230. These types of bag-in-containershave the advantage of being reusable, but they are very expensive andlabour-intensive to produce.

More recent developments focused on the production of “integrallyblow-moulded bag-in-containers” thus avoiding the labour-intensive stepof assembling the bag into the container, by blow-moulding a polymericmultilayer preform into a container comprising an inner layer and anouter layer, such that the adhesion between the inner and the outerlayers of the thus produced container is sufficiently weak to readilydelaminate upon introduction of a gas at the interface. The “innerlayer” and “outer layer” may each consist of a single layer or aplurality of layers, but can in any case readily be identified, at leastupon determination. Said technology involves many challenges and manyalternative solutions were proposed.

The multilayer preform may be extruded or injection moulded (cf. U.S.Pat. No. 6,238,201, JPA10128833, JPA11010719, JPA9208688, U.S. Pat. No.6,649,121. When the former method is advantageous in terms ofproductivity, the latter is preferable when wall thickness accuracy isrequired, typically in containers for dispensing beverage.

Preforms for the production of integrally blow-moulded bag-in-containersclearly differ from preforms for the production of blow-mouldedco-layered containers, wherein the various layers of the container arenot meant to delaminate, in the thickness of the layers. Abag-in-container is comprised of an outer structural envelope containinga flexible, collapsible bag. It follows that the outer layer of thecontainer is substantially thicker than the inner bag. This samerelationship can of course be found in the preform as well, which arecharacterized by an inner layer being substantially thinner than theouter layer. Moreover, in some cases, the preform already comprisedvents which are never present in preforms for the production ofco-layered containers (cf. EPA1356915).

The formation of the vents fluidly connecting the space or interfacebetween bag and bottle to the atmosphere remains a critical step inintegrally blow-moulded bag-in-containers and several solutions wereproposed in e.g., U.S. Pat. Nos. 5,301,838, and, 5,407,629, JPA5213373,JPA8001761, EPA1356915, U.S. Pat. No. 6,649,121, JPA10180853. Oneredundant problem with integrally blow-moulded bag-in-containers is thechoice of materials for the inner and outer layers which must beselected according to strict criteria of compatibility in terms ofprocessing on the one hand and, on the other hand, of incompatibility interms of adhesion. These criteria are sometimes difficult to fulfil incombination as illustrated below. The thermal properties of thematerials of the inner and outer layers should be as close as possiblefor the blow-moulding step, but should differ sufficiently for theinjection moulding production of an integral multilayer preform.

Beside the thermal properties, it should be ensured that the inner andouter layers form a weak interface to ensure proper delamination of theinner layer from the outer layer upon use; JP2005047172 states that theinner and outer layers should be made of “mutually non-adhesivesynthetic resins.”

As an interface between inner and outer layer is inevitably formed uponblow-moulding, which strength may not always be as uniform as one coulddesire, due to various phenomena during the blow-moulding stage, such aslocal heat gradients, differential resin stretch and flow rates atdifferent points of the vessel, etc., the delamination of the inner bagfrom the outer layer is not always perfectly controllable. It has beenobserved that the two layers may delaminate preferentially on one sideof the bag-in-container due to a local weakness of the interface and, asthe bag starts shrinking asymmetrically bending and folding with therisk of forming pockets full of liquid separated from the container'smouth. If this happens, the bag-in-container cannot be used anymorealthough it can still contain a considerable amount of liquid.

JP4267727 suggests to fix the inner and outer layers at their bottomswithout disclosing how to achieve this. In Japanese Utility ModelJP048519, one end of a co-extruded multilayer parison is pinched offsuch that mutually engaging corrugations are formed, and fixing thestructure through an additional device prior to blow-moulding. U.S. Pat.No. 6,649,121 proposes to fix the inner bag to the outer layer byforming at the bottom of the inner layer of the preform to beblow-moulded into the bag-in-container, a protrusion which fits athrough hole formed at the bottom of the outer layer and engagesmechanically on the outer surface of the outer layer. This geometryappears to be maintained through the blow-moulding process by limitingthe axial stretch of the bottom area of the container through thedriving downwards of a stretching rod.

Co-extruded parisons as described is the foregoing Japanese UtilityModel do not allow the same wall thickness control as when injectionmoulded preforms are used, which is required is applications in thefield of pressurized beverage dispense bag-in-containers. The solutionproposed in U.S. Pat. No. 6,649,121 applies to bag-in-containers whereinthe liquid contained in the bag is dispensed by decreasing the pressurein the bag and does not allow to dispense liquid by injection of apressurized gas at a point of the interface between the inner and outerlayers because the inner layer's protrusion is not meant to engagehermetically on the outer surface of the outer layer. Indeed, thesolution proposed in U.S. Pat. No. 6,649,121 includes that air mustpenetrate through the interstice between the protrusion and the throughhole wall to compensate for the growing pressure drop as a gap is formedbetween the inner and outer layers upon extracting the liquid by vacuumand the resuming shrinking of the bag.

It follows from the foregoing that there remains a need in the art foran integrally blow-moulded bag-in-container that allows controlleddelamination of the inner bag from the outer container upon injection ofa pressurized gas at the interface thereof.

SUMMARY OF THE INVENTION

The present invention is defined in the appended independent claims.Preferred embodiments are defined in the dependent claims. In particularthe present invention relates to an integrally blow-mouldedbag-in-container obtainable by blow-moulding an injection mouldedmulti-layer preform. The bag-in-container includes an inner layerforming the bag and an outer layer forming the container, and a singleopening, the mouth, fluidly connecting the volume defined by the bag tothe atmosphere. The container further includes at least one interfacevent fluidly connecting the interface between inner and outer layers tothe atmosphere, wherein the bag is anchored to the outer layer at atleast one point remote from the single opening.

It also concerns a process for producing a bag-in-container as describedabove comprising the following steps:

-   -   providing a polymer preform comprising two layers;    -   bringing the preform to blow-moulding temperature;    -   blow-moulding the thus heated preform to form a        bag-in-container;        wherein during the process, the inner bag is anchored to the        outer layer at at least one point remote from the        bag-in-container's mouth.

The anchoring may be realized through locally enhanced mechanical,physical, or chemical adhesion between the inner and outer layers, orcombinations thereof.

Locally enhanced mechanical adhesion may be provided with ablow-moulding tool comprising for example a sump or depression in whichinner and outer layers engage daring the blow-moulding process and thusbecome interlocked.

The sump or depression may be provided in the blow-moulding tool byinserting therein a chime defining said sump or depression. Wheneffecting the blow-moulding operation with the chime incorporated in theblow-moulding tool the interlocking between the inner and outer layersis achieved and additionally the chime is readily fixed to thecontainer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional representation of a firstembodiment of a preform according to the present invention and thebag-in-container obtained after blow-moulding thereof.

FIG. 1B: is a schematic cross-sectional representation of a secondembodiment of a preform according to the present invention and thebag-in-container obtained after blow-moulding thereof.

FIG. 2: is a schematic representation of a blow-moulding tool with abag-in-container therein.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to appended FIGS. 1A and 1B, there is illustrated anintegrally blow-moulded bag-in-container (2) and a preform (1)&(1′) forits manufacturing. The preform (1) comprises an inner layer (11) and anouter layer (12) joined at least at the level of the neck region (6) byan interface (shown on the right hand side). The region between innerand outer layers (11) and (12) may either consist of an interface (14)wherein the two layers are substantially contacting each other, orcomprise a gap (14′) in fluid communication with at least one vent (3).Said vent (3) comprises an opening to the atmosphere in (4).

Many vent geometries have been disclosed and it is not critical whichgeometry is selected. It is preferred, however, that the vent be locatedadjacent to, and oriented coaxially with said preform's mouth (5) asillustrated in FIG. 1. More preferably, the vents have the shape of awedge with the broad side at the level of the opening (4) thereof andgetting thinner as it penetrates deeper into the vessel, until the twolayers meet to form an interface (14) at least at the level of the neckregion. This geometry allows for a more efficient and reproducibledelamination of the inner bag upon use of the bag-in-container. Thecontainer may comprise one or several vents evenly distributed aroundthe lip of the bag-in-container's mouth. Several vents are advantageousas they permit the interface of the inner and outer layers (21) and (22)of the bag-in-container (2) to release more evenly upon blowingpressurized gas through said vents. Preferably, the preform comprisestwo vents opening at the vessel's mouth lip at diametrically opposedpositions. More preferably, three, and most preferably, at least fourvents open at regular intervals of the mouth lip.

The preform may consists of an assembly of two independent injectionmoulded preforms (11) and (12) produced independently from one anotherand thereafter assembled such that the inner preform (11) fits into theouter preform (12). This solution allows for greater freedom in thedesign of the neck and vents, as well as in the choice of materialsconstituting each preform component. Alternatively, it can be anintegral preform obtained by injection moulding one layer on top of theother. The latter embodiment is advantageous over the assembled preformin that it comprises no assembly step and one production station only isrequired for the preform fabrication. On the other hand, the design ofthe vents in particular is restricted and the respective meltingtemperatures of the inner and outer layers must be carefully matcheddepending on which layer is injected first; the rule of thumb being thatthe layer being injected first generally requires a higher meltingtemperature.

The inner and outer layers of the preform (1) may consist of differentmaterials or the same material. In case different materials are used,some requirements must be fulfilled depending on the process parametersin the injection moulding of the preform as well as in the blow-mouldingof the bag-in-container. It is important of course that both materialsmay be processed in a rather similar process window and that they willnot form too strong an interface which would not satisfactorily releaseupon injecting pressurized gas at the interface.

Alternatively and surprisingly, good results can be obtained also withpreforms wherein both inner and outer layers consist of the samematerial. Particularly is case of integral, over-moulded preforms, it isgenerally believed that better results are obtained withsemi-crystalline polymers.

The same polymer is considered in contact on either side of theinterface between the inner and outer layers in the following cases:

-   -   inner and outer layers consist of the same material (e.g.,        PET_(inner)PET_(outer), regardless of the specific grade of each        PET); or    -   the inner and outer layers consist of a blend or copolymer        having at least one polymer in common, provided said polymer in        common is at the interface, whilst the differing polymer is        substantially absent of said interface (e.g., (0.85 PET+0.15        PA6)_(inner)(0.8 PET+0.2 PE)_(outer).        The presence in a layer of low amounts of additives is not        regarded as rendering the material different, so far as they do        not alter the interface substantially.

Preferred materials for the preform and bag-in-container of the presentinvention are polyesters like PET, PEN, PTT, PTN; polyamides like PA6,PA66, PA11, PA12; polyolefins like PE, PP; EVOH; biodegradable polymerslike polyglycol acetate (PGAc), Polylactic acid (PLA); and copolymersand blends thereof. In case different materials are used for the innerand outer layers, their optimal blow-moulding temperature should notdiffer from one another by more than 70° C., preferably 40° C., mostpreferably 10° C., and ideally should have the same blow-mouldingtemperature.

The two layers (11) and (12) of the preform may be connected by aninterface (14) throughout substantially the whole inner surface of theouter layer. Inversely, they may be separated over a substantial area ofthe preform's body by a gap (14) containing air and which is in fluidcommunication with at least one interface vent (3). The latterembodiment is easier to realize when using a preform assembly designedsuch that the inner preform is firmly fixed to the outer preform at theneck region (6) and a substantial gap (14) may thus be formed betweeninner and outer layers (11) and (12).

The bag-in-container (2) of the present invention is obtained byproviding a preform as described above; bringing the inner and outerlayers of said preform to blow-moulding temperature; fixing the thusheated preform at the level of the neck region with fixing means in theblow-moulding tool; and blow-moulding the thus heated preform to form abag-in-container, such that the inner layer is locally anchored to theouter layer at a location (7) remote from the bag-in-container's neckregion.

The inner and outer layers (21) and (22) of the thus obtainedbag-in-container are connected to one another by an interface (24) oversubstantially the whole of the inner surface of the outer layer. Saidinterface (24) is in fluid communication with the atmosphere through thevents (3), which maintained their original geometry through theblow-moulding process since the neck region of the preform where thevents are located is held firm by the fixing means and is not stretchedduring blowing.

It is essential that the interface (24) between inner and outer layers(21) and (22) releases upon blowing pressurized gas through the vents ina consistent and reproducible manner. The success of said operationdepends on a number of parameters, in particular, on the interfacialadhesive strength, the number, geometry, and distribution of the vents,the pressure of the gas injected, and the inner bag stability. Thelatter can be substantially improved by fixing the inner layer to theouter layer at a location remote from the neck region and mouth of thebag-in-container, such that the interface between inner and outer layerswill not release at said anchoring point upon injecting pressurized gasat a point of the interface. The bag is thus fixed at two points remotefrom one another; the neck region and the anchoring point. This allowsto better control the collapse of the bag, which is essential for areliable and reproducible operation of the bag-in-container.

The anchoring of the inner to the outer layers may be provided by alocally enhanced mechanical, physical, or physical adhesion. Mechanicaladhesion includes any interaction between inner and outer layers at allscales spanning from macroscopic mechanical interlocking tocross-crystallinity as well as molecular inter-diffusion across theinterface, all phenomena well known to the person skilled in the art.Physical and chemical adhesion is also well studied and involvesdispersive forces (e.g., London and Keaton forces), acid baseinteractions (sometimes also referred to as polar forces), hydrogenbonds, and covalent bonds.

All, but macroscopic interlocking, of the above adhesion mechanisms aretemperature dependent and may be locally promoted, e.g., by controllingthe local temperature of the interface at the point where anchoring isdesired. In case of preform assemblies, an adhesive may be applied atthe desired anchoring point prior to fitting the inner preform into theouter one. The adhesive must resist the blow-moulding temperature and becompliant enough to stretch with the preform upon blowing.

Macroscopic interlocking may be achieved by using a blow-moulding toolcomprising a sump or depression at the desired anchoring point,preferably at the bottom of the container as illustrated in FIG. 1. Uponblow-moulding the heated preform expands and the inner and outer layersengage into the sump. The angle, α, formed by the sump wall with thesurrounding container's body wall maybe greater to or equal to 90degrees, in which case an anchoring point is formed by enhanced frictionbetween the inner and outer layer at the level of the thus producedprotrusion or, alternatively, the angle can be smaller than 90 degrees,in which case a mechanical interlocking of the two layers is formed likea rivet.

Preferably a stretching rod drives the preform downwards during theblow-moulding process to promote longitudinal stretching and to ensurethat good contact of the preform with the tool's wall is effected at thedesired point of anchoring.

In the case the angle, α, formed by the sump wall with the surroundingcontainer's body wall is smaller than 90 degrees and the mechanicalinterlocking of the two layers is formed like a rivet, the anchoringpoint comprises an undercut. The creation of this undercut can beachieved in several methods, some of which are described below.According to a first method, the undercut is created by using ablow-moulding tool comprising two half-moulds that are only partiallyclosed at the location of the sump, the side walls of the half-moulds atthe sump location defining a negative of the anchoring point to becreated. The preform is driven down in the sump by means of a stretchingrod, where after both half-moulds are moved towards each other toentirely close the mould, creating the undercut.According to another method, a blow-moulding tool is used comprisingaxially moving pins that can be introduced in the mould cavity duringblow-moulding, allowing creation of the undercut.According to yet another method, the blow-moulding tool with half-mouldsdefining a sump negative to the anchoring point to be created. Thepreform beind driven into the sump by means of the fluid pressureapplied during blow-moulding thereof. In this method, a stretching rodmay be used that either stops at a position distant from the sump orthat extends into the sump. In the last case, it is preferred to use astretching rod provided with a central fluid channel and lateralopenings at its distal end (the end extending in the blow-moulding tool)that extends into the sump during stretching, such that part of thefluid used to stretch the preform is guided through the fluid channeland the lateral openings to facilitate stretching of the preform intothe sump and against the inner wall the mould cavity defining the sump.FIG. 2 schematically represents a blow-moulding tool with providedtherein a chime comprising said sump or depression at the desiredanchoring point. This chime is inserted in the blow-moulding tool priorto blow-moulding the preform, such that upon blow moulding the heatedpreform expands and the inner and outer layers engage into the sump. Inthis manner, the desired macroscopic interlocking is achieved andadditionally a chime is provided on the container. In the case the sumpdefined by the chime is designed for the creation of an anchoring pointin the form of a rivet, the anchoring point can successfully be createdby means of fluid pressure forcing the material of the preform into thesump. Both methods applying a stretching rod and not applying astretching rod can be used.

A release agent may be applied at the interface on either or bothsurfaces of the inner and outer layer, which are to form the interfaceof the bag-in-container. In the case the outer layer is injectionmoulded into the inner layer, the release agent can be applied at theouter surface of the inner layer prior to moulding the outer layer. Anyrelease agents available on the market and best adapted to the materialused for the preform and resisting the blowing temperatures, likesilicon- or PTFE-based release agents (e.g., Freekote) may be used. Therelease agent may be applied just prior to loading the preforms into theblowmoulding unit, or the preforms may be supplied pretreated.

The application of a release agent is particularly beneficial withrespect to the design of the inner layer. Indeed, lowering theinterferential adhesive strength facilitates delamination of the innerlayer from the outer layer and hence reduces stress exerted on the innerlayer upon delamination, as such the inner layer can be designed verythin and flexible without risking that the inner layer is damaged upondelamination. Clearly, the flexibility of the inner bag is a keyparameter for the liquid dispensing and moreover costs savings can beachieved in terms on material savings when the inner layer can bedesigned very thin.

We claim:
 1. A process for producing a bag-in-container, thebag-in-container is obtained by blow-moulding an injection mouldedmulti-layer preform and includes: an inner layer forming the bag and anouter layer forming the container; a single opening, the mouth, fluidlyconnecting the volume defined by the bag to the atmosphere; and at leastone interface vent fluidly connecting the interface between inner andouter layers to the atmosphere, wherein the bag is anchored to the outerlayer at least at one point remote from the single opening and interfacevent, the process for producing the bag-in-container comprising thefollowing steps: providing an injection moulded polymer preformcomprising two layers; bringing the preform to blow-mouldingtemperature; and blow-moulding the heated preform to form abag-in-container, wherein, during the process, the anchoring point isobtained by local thermal control of the layers in order to enhancechemical or physical adhesion between the inner and outer layers.
 2. Theprocess according to claim 1, wherein the anchoring point is obtained bylocally enhanced mechanical adhesion between the inner and outer layers.3. The process according to claim 2, wherein mechanical adhesion islocally enhanced by a protrusion formed by both inner and outer layersengaging in a sump formed in a tool.